The subject matter disclosed herein relates to a detachable fastening device such as an expansion clip or insertion expansion clip. The detachable fastening device is intended to hold an assembly part such as a motor vehicle part, preferably a motor vehicle part exposed to vibrations, such as an absorption mass, firmly and immovably in a receptacle holding the assembly part, in particular a vehicle autobody. A motor vehicle radiator can be considered to be an assembly part whose fastening devices must withstand high vibrational loads. Usually the autobody-side fastening of the assembly part is made by means of screwing into a threaded bore on the motor vehicle body. However, it has been shown that the screw connection cannot provide a sufficient play-free fatigue endurance limit. The motor vehicle industry uses the so-called “shaker test” to examine the stability of the autobody-side connection of the assembly part, in which accelerating load forces of up to 5 g act on the assembly part. In motor vehicle radiators of the usual size, maximum loads of 150 kg should be withstood over a fairly long period.
An example for a generic detachable fastening device is known from German Patent Reference DE 10 2007 016 484 A1 which discloses an insertion expansion clip. The expansion clip comprises a base or a sleeve-like body part having a contact flange, three clamping arms formed on the contact flange which are initially expanded resiliently in the radial direction in an inward deforming manner for locking into a clamping position before then snapping outwards resiliently in the radial direction. In order to achieve the locking, the clamping arms snap in an expanding or spreading manner into the receptacle of the motor vehicle autobody, wherein the assembly part to be fastened is locked between the contact flange of the base of the expansion clip and the motor vehicle autobody. An axial insertion opening is formed in the contact flange into which a blocking or expanding mandrel is inserted when the expansion clip is disposed in the clamping position. The three clamping arms each have a blocking or expanding actuation section. The blocking or expanding mandrel received in the insertion opening extends in the axial direction as far as the blocking or expanding actuation section and comes into contact engagement therewith, which is why the blocking or expanding mandrel prevents an expanding or spreading deformation of the clamping arms from their clamping position radially inwards or even widens the clamping arms in an expanding or spreading manner further into the clamping position in the radial latching direction. The detachable fastening device ensures by means of the blocking or expanding mandrel that the clamping arms do not open autonomously when loads act on the assembly part or the vehicle body and an unintentional release of the assembly part from the motor vehicle body is avoided.
The release of the fastening device is enabled by access to the clamping arms from outside. As a result of the limited installation space, in particular in the engine compartment, in particular in the case of blind hole receptacles, the accessibility required for release is not readily ensured so that the usability of the known expansion clip is limited.
It is one object of the invention to overcome the disadvantages of the prior art, in particular to provide a generic detachable fastening device for an assembly part such as a motor vehicle part which enables a simple release of the fastening device itself even if there is no possibility for access from the outside to the detachable fastening device.